REALLY slow high torque windmill

[nwcpro]

   I have a gear-reduced 24 volt motor that produces A LOT of energy with very little effort, and I would like to use it as a windmill generator.  Is there a rotor or windmill design that will turn this thing at, say 100 RPM?  The motor is rated at 20 amps at 184 RPM, and from my tests, I beleive it!  It will produce serious arcs when turned by hand.

   The motor turns with the weight of a pipe wrench on it, so it isn't THAT hard to turn.  I was wondering if maybe a design like the classic water pumps would work.

   Any advice would be appreciated

[Flux]

How about a windflower.

http://www.windmission.dk/

[finnsawyer]

Ideally, you should determine what the motor can do as a generator.  That means connecting it up to another motor and determining its output voltage and current as a function of rpm for different loads.  Can you turn it with a large drill, for example?  In principle you could also get an idea of its efficiency by measuring the power into the driving motor.  Once you have all that data you can match it to the proper size blade assembly.  Admittedly not easy.

Another thing you can do is hang a wooden arm straight off of it and by hanging weights on it determine the starting torque it needs.  Torque equals weight times the length between the weight and the center of the shaft.  This is easy to do and gives an indication of the size prop you need at a given start up wind speed.

If nothing else you should try to determine the open circuit voltage as a function of rpm in order to make sure you can get usable voltage out (> 14 volts).  

[nwcpro]

   Well, granted it isn't very accurate, but if you hang a large pipe wrench (24") off the shaft, it turns on it's own.  As for output voltage and current, I hooked up a 19.2 drill to it and it produced 24-30 volts open circuit depending on RPM.  With any load at all, it killed the drill instantly.  I turned it by hand with the same pipewrench and it ran a set of 14" radiator fans to thier rated speed (LOT'S of air!)

   My concern is getting a design to work with the slow speeds this thing needs.  It's only rated at 180 RPM.  I would love to remove the gear reduction, but that would cost me some seriously heavy duty bearings and a nice input shaft.  The actual motor input is just a tiny gear.

   Thanks for all the advice!

[Norm]

 Hook a 12volt headlight to it....about a 3 inch pulley on the shaft...wind a small steel cable around the pulley attach weights until the light reaches its normal brilliance, then calculate the

ft/lbs.per minute to obtain that current, from there I'm sure there are a couple of people on the board that know of multibladed windmills that would power it.

                Have Fun!

                   ( :>) Norm.

[fuzz]

Take a look inside the gearbox, most gearboxes don't accept input on output shaft.

If gears near the motor are made of plastic's (Acetal) it won't last long.

fuzz

[erne]

If you go to the photos in my section, you will find a multi bladed horse power chart for aeromotor mills. there is a photo of my genny there also. It turns 120 rpm in a 30mph wind.---erne --ps a 24 ft mill puts out 38 horses @ 30 mph.(not on the chart)

[nwcpro]

No problem with the gears.  They are all heavy straight-tooth with nice support bearings.

[Ungrounded Lightning Rod]

Sounds like a good candidate for a genny on a Sandia Savonius vertical-axis mill.  Low speed, high torque, no yawing.

Only gets about 2/3 of the theoretically extractable energy from the wind.  But that just means you make it half-again as big and use stronger guy lines.  B-)

(Furling may be an issue.)

[Norm]

  I was looking at your files when was that mill blade.tif file posted?...I must have missed it....that's quite a hunk of machinery there! What size is it?

      ( :>) Norm.

[juiced]

what did this motor come from? sounds very interesting.

[Flux]

Perhaps a sailwing would be worth a try.  They are fairly well self regulating in higher winds.

Flux

[tecker]

 Turning a gearhead motor backwards is tricky . the bearings on the output shaft not designed for drive and have a tendency to kick out at the bottom with torque that puts a bind on the bearings and wears unevenly adding  up to friction . the brushes on the motor will get hot with current the armature will get very hot when included in a circuit .It's like holding the shaft still and hitting the switch.

[nwcpro]

   Well, maybe I'm just stubborn, but I still don't think the bearings will be a problem.  This unit came from an old powered wheelchair.  I used to work on them for a while, and I can tell you that they get driven almost as much as they drive.  They have to be built for both stop and go and long run operations.  I've had my eye on these motors for quite some time, but they are usually encased in the transaxle and the output shaft of the actual motor is terribly small (like 1/4" X 1/2" total).  This unit is almost the same internally, but has a nice 1" output shaft outside the gearbox.  Oddly, it's suprisingly easy to turn despite the gearing.

   As for the headlight trick:  I tried that just for a joke and burned out the headlight - and my eyes - while turning the shaft by hand with a wrench(oops!).

   I still see the main problem being getting it started.  It's much like a cogging issue (I think?).  It takes twice as much torque to start the motor as it does to keep it going.  I thought of setting up a small wind sensor that would kick in a start current when the wind stayed above a certain speed for a certain amount of time, but that gets very complex very fast.

   In the end, I think I'm just going to have to build a really large, really slow windmill design and see what happens.  If I can keep the costs down, why not?

[RatOmeter]

This unit came from an old powered wheelchair.  I used to work on them for a while, and I can tell you that they get driven almost as much as they drive.

I agree.  Played with a Jazzy brand power chair for about a week.  It has a electrically operated brake which is only engaged when not in motion and (I'm pretty sure that) all of the dynamic braking is regenerative.

The one thing I don't have a good feel for is how well those motors are designed to withstand radial loading, but I think you can take that into account when building it into a wind gen setup.

[wildbill hickup]

Off the wind subject for a second (sorry guys), but wouldn't somthing like this be great for a low head (or volume) hydro plant?

[nwcpro]

You know, that was my other thought.  However, not having any water to work with (or, to be honest, no wind either), I put that on a back burner.

   The trick is to translate speed into torque for the application.  This thing would produce usable energy at 50-60 RPM.

[hevan]

Sounds beautiful.